1. Field of the Invention
The invention relates to the isolation, selection, and application of novel strains of bacteria which have the ability to control the weed downy brome in small grain crops without deleteriously affecting the crop.
2. Description of the Art
Downy brome (Bromus tectorum) and the closely related species Japanese brome (B. japonicus), and cheat (B. secalinus), hereinafter referred to collectively as downy brome, are winter annual grass weeds which cause serious reductions in small grain crop yields by competing with crops for moisture, space, and nutrients. This results in significant economic losses. The spread of these weeds has increased in recent years because conservation tillage systems make these weeds more difficult to control than conventional tillage systems.
Downy brome is a major weed of winter crops especially winter wheat. It can also be a problem in winter barley but is of less economic importance because winter barley acreage is relatively small. Winter wheat yield losses can be as high as 45% with 84-100 downy brome weeds/yard.sup.2 while losses of 10% occur with a reduced downy brome infestation (Stahlman, Kansas Agricultural Experiment Station 87-69-S, 1986). Downy brome control of greater than 80% with the herbicide dicloflop resulted in 129 to 263% increased grain yield when compared to the control (Thill et al. In: STEEP Conservation Concepts and Accomplishments, L. F. Elliott et al. (eds.), pages 275-287, Washington State University Press (1987)). However, no chemical herbicide presently available gives consistent control against this weed.
While use of antagonistic microorganisms for biological control of some weeds have been reported, no bacterial strain has been previously found which would control the weed downy brome; additionally, no procedure for the selection of bacteria which inhibit downy brome in small grain crops has been reported. Because the physiological characteristics required for a bacterial strain to control weeds are very specific as to (1) the weed to be controlled; (2) the mode of action of weed control; (3) the activity and ecological niche of the microorganism; and (4) cultural practices and soil and climatic conditions favorable for control, information about microorganism treatments for control of weeds other than downy brome cannot be used to predict strains of microorganisms which would reduce downy brome under field conditions or predict criteria for selecting such strains.